Magnitude-Frequency Distribution of Rainfall-Triggered Landslide Erosion in Kaoping River Watershed, Southern Taiwan

[[abstract]]Magnitude-frequency of landslide erosion is a critical component to investigate the long-term erosion rate, landscape evolution, and natural hazard in tropical and mountainous area. In this study, the relationship between magnitude and temporal frequency for rainfall-triggered landslide erosion was been quantified in the Kaoping River watershed, southern Taiwan. The magnitude of landslide erosion was estimated by using multi-temporal landslide inventory with volume-area relations. The long-term frequency of landslide was derived from the record of 244 storms in 53 years and using hydrological frequency analysis by 6 types of probability distribution function. Then, we utilized the concept of an expectation of landslide erosion (EXLE) to explore the contributions of different rainfall intensity and to analysis the landslide erosion rate. The results show that the magnitude-frequency distributions show negative and piecewise power-law functions and the EXLE increase over the rainfall intensity. This reveals that landslide erosion triggered by intensive-extreme rainfall is more important than it triggered by moderate-frequent rainfall. Then, the landslide erosion rate is estimated to be 2.99 - 5.27 mm yr-1 in which rainfall with return period >= 10 years contributes 56-75% of total landslide erosion in the Kaoping River watershed. Analyzing the magnitude-frequency distribution is a reliable method that can quantify the contribution of landslide by different rainfall intensity and can avoid the uncertainty resulting from extreme event in estimation of landslide erosion rate